The photochemical and spectroscopic properties of the isomeric retinals, synthetic analogs, the visual protein rhodopsin, and synthetic pigments will be examined. In particular, we are interested in the protein-chromophore interactions in rhodopsin and the effects that these interactions have upon the photochemistry of the 11-cis retinyl chromophore in the visual protein. Aspects of the cis-trans photoisomerization of 11-cis retinal have been examined, including a study of the effect of ground state conformation on phi PI. The nature of the protein-chromophore interactions in rhodopsin are being investigated using high resolution infrared spectroscopy. Difference spectra obtained by subtraction of infrared spectra of opsin from rhodopsin and of rhodopsin from several of the bleaching intermediates obtained upon low temperature photolysis will be recorded. Information obtained from infrared and photochemical studies by synthetic pigments, i.e., isorhodopsin and 9,13-isorhodopsin, should be of value in understanding the nature of the chromophore's environment.